I am sure there are better softwares, but unless you are willing to spend hundreds of $, I would highly recommend spriter. Spriter is quite straightforward and simple, so if you are having problems with it, expect a much more deeper learning curve with many of the other softwares out there. You should check out their Youtube channel and see how it works.
Trust me, you do not want a software that imports only one whole image and animates from it. It will be a nightmare to to manually set all the vector points to avoid stretching and weird overlaps. But you should look around for some alternatives and than look at the tutorials to see which is best suited to your needs and skill level.